I'm in a good mood, so I guess I can post what I've observed when playing Yuki in the arcade today.
b/n/f+ CD when up close
Basic throw. Moving on...
f+ A; df+ C; b+ B; f+ D
I did not test this move out yet, so I don't know what it looks like or what it does. Sorry.
Dogou Sou Ken
close standing C; f+ C
Basic combo stuff, you know what to do.
Think of it as a fireball projectile. A fast-moving, invisible fireball projectile. Many characters can crouch under it, but since the projectile is totally invisible, they might be fooled and stand up at the wrong moment. When powered up with the A-version Memory Card Slash, he fires 3 projectiles in a row. That'll really keep the opponent away.
Yuki strikes diagonally upwards, with a streaking fiery light. This move might serve as anti-air, but I don't really like the regular version of this move. When powered up with the C-version Memory Card Slash, YUKI TURNS INTO A GLOWING BLUE VERSION OF DUKE EDWARDS AND DOES THE REAL SUBMARINE SCREW. This move now has priority, invincibility, and does good damage. However, if this move whiffs or is blocked, Yuki's in trouble.
Yuki travels quickly forward and performs an electric punch. Keep in mind that, unlike other horizontal dashing moves like Terry's Burning Knuckle, Yuki is vulnerable when he travels forward, until the end where he delivers that punch. There are still uses for this move, if you can time it right. qcb+ A is good in combos.
Every time I tried to use the regular version of this move, Yuki hopped forward a little bit and... that was it. I got punished after that. However, when powered up with the B-version Memory Card Slash, he jumps farther forward and the move actually connects when I do it; it looks like he slashes the opponent with knives or something like that, which knocks the opponent in the air. I don't know all the properties of this move, but it looks interesting. Probably not a move to use all the time, though.
mid-air qcb+ A/C
ZOMG, an air dash! WTF IS THIS GUILTY GEAR???
mid-air qcb+ B/D
Yuki disappears, and when he reappears on the ground directly below, a lightning bolt instantly appears. I suspect that he has invulnerability while he is invisible. I like using this after Riding Hero. Nice for countering or cross-ups. When powered up with the D-version Memory Card Slash, there are more lightning bolts which cover more area and do up to 4 hits.
Fire Suplex Hold
hcb,f+ A/C when up close
This move can only be performed after you've done the Start-version Memory Card Slash. He does what looks like the regular Fire Suplex, but then he holds you there and grinds you into the ground for more damage (kinda like the Shermie Flash). There's the old-school Fatal Fury sign consisting of a hand and a button that prompts you to push a button rapidly. I'm not sure whether it's for Yuki (to keep the move going) or for the opponent (to get out of the move).
Memory Card Slash
Yuki creates a small flash of light, which charges up certain special moves (see above). You are vulnerable when performing Memory Card Flash, so be careful. Memory Card Flash only works once and may wear off over time, so if you do a powered-up special move or if you wait too long, you'll have to perform that particular Memory Card Flash again. You can store multiple power-ups of different types (such as one A-version power-up and one C-version power-up), but I don't know if you can store multiple power-ups of the same type (such as two A-version power-ups).
Chou Do Kyuu 100 Mega Beam
Yuki rises up in the air and fires a huge beam of energy at the opponent. Yup, Yuki's a beamer. Doesn't do a lot of damage for a super, but that's perfectly all right since it's a beam. Be careful though, because although it may not look like it, the opponent does have time to block... unless he/she is in the air or doing a move with some recovery. Then the hit is almost guaranteed. This move consumes 1 Super Bar.
Chou Do Kyuu Neo-Geo Ranbu
Just like the move suggests, this move is an auto-combo "Ranbu" super along the lines of Ryo's Ryuuko Ranbu, Kim's Hou'ou Kyaku, or Iori's Maiden Masher. This move consumes 2 Super Bars.
Chou Do Kyuu Status Up
This move powers up Yuki, but I don't know exactly what it's supposed to power up. More investigation will be needed here. This move consumes 2 Super Bars.
Chou Do Kyuu MAX330 Mega Beam
Just like the Chou Do Kyuu 100 Mega Beam, except it does more damage. This move consumes 3 Super Bars.
Here's the only real combo I managed to do with Yuki:
close standing C; f+ C; qcb+ A; qcb,qcb+ A/C
You can stop right after the qcb+ A, since I never actually managed to make the Mega Beam connect even though it counts as a Super Cancel. Then again, the opponent was in the corner every time I used the Mega Beam in that combo, so maybe that's why.
There are 3 conditions to performing the Secret D-Assault:
1.) Ai must be your second character.
2.) D-Assault must be enabled.
3.) There are three Memory Card Slashes you need: one with A, one with B, and one with the Start button. I'm not sure which, but you must either do one of these or all three. When I performed the D-Assault, I did all three Memory Card Slashes just to be on the safe side.
I haven't confirmed this, but I have suspicions that everything is reset when you get hit by the opponent (even with a jab), so you'd have to do the Memory Card Slashes all over again. For some odd reason, this secret D-Assault was difficult to perform for me.
Once you've met the conditions: qcb,hcf+ AE
If this move connects, Yuki and Ai "unite" with a heart-shaped glow to summon Atomic Guy (of "King of the Monsters" fame). Yuki will only be Atomic Guy for a short while, so be quick. Press A or C to punch, and B or D to kick. Press ABC to form an electric field around Atomic Guy (Ã la Blanka). Be warned: Atomic Guy will turn back into Yuki right after the ABC move. I think something happens when you press back on the joystick twice, but I haven't tested that out yet.